The National Weather Service released another excessive heat warning Tuesday for much of Washington State and Oregon which will remain in effect for the next few days. There is also heat notice in the northeast, from Philadelphia to Boston. Here’s what you need to know about these heat waves:
What causes a heat wave?
In most parts of the country, temperatures must be above the historical average in an area for two or more days before the “heat wave” label is applied to a heat wave, according to the National Weather Service. But the definition may vary by region; to North-east, it is defined as three consecutive days in the 90s or more.
Heat waves start when the high pressure in the atmosphere moves and pushes hot air towards the ground. This air heats up more as it is compressed and we start to feel a lot hotter.
The high pressure system pressing down on the ground expands vertically, forcing other weather systems to change course. It even minimizes wind and cloud cover, making the air more stuffy. This is also why a heat wave parks in an area for several days or more.
What is a heated dome?
As the soil warms up, it loses moisture, making it even easier to heat. And in the drought-ravaged west, there is a lot of heat to be trapped by the high pressure system.
As this trapped heat continues to heat up, the system acts like a lid on a pot, earning it the name “hot dome”. In the Pacific Northwest, heat and drought work together, exacerbating the problem and pushing down temperature records day after day.
What places in North America are currently experiencing a heat wave?
One of the hottest cities on the mainland on Monday was Salem, Oregon, about 45 miles southwest of Portland, where the high temperature reaches 117 degrees Fahrenheit in the afternoon, a record for the city, according to the National Weather Service.
Canada broke a national heat record on Sunday when the temperature in a small town in British Columbia hit nearly 116 degrees, breaking an 84-year-old record of nearly 3 degrees.
The northeast, under a separate weather system from the northwest, is also in the middle of a three-day heat wave that is expected to end on Thursday. Boston reached 97 degrees Monday, tying its record for that date, the National Weather Service reported.
Why is it hotter than normal in North America?
We have known for a long time that the world has warmed by more than one degree Celsius (about 1.8 degrees Fahrenheit) since 1900, and that the rate of warming has accelerated in recent decades. The warmer baseline contributes to extreme weather events and helps make periods of extreme heat more frequent, longer and more intense.
When will the heat wave end?
Forecasters say temperatures will remain unusually warm next week in the Pacific Northwest.
In Portland, temperatures have moderated somewhat but are expected to reach the mid-1980s later in the week, said Clinton Rockey, a meteorologist with the National Weather Service in Portland. Temperatures will remain 10 to 20 degrees above average at least until next Tuesday.
How can I protect myself against possible power outages?
In Seattle, where until this month official weather stations for the last century had recorded just three days exceeding 100 degrees, many other residents have recently purchased air conditioning units. While there have been no major blackouts in the Pacific Northwest, the power grid could be overloaded with increased energy demand to cool and dehumidify buildings.
To help reduce demand, consider raising the thermostat a few degrees and closing shades and shades. Avoid using large appliances like ovens, washing machines, and dryers during the hottest part of the day, and turn off all unused lights and electronics. As water heating accounts for around 18% of the energy consumed in your home, consider shorter or colder showers, the Department of Energy offers.